Bring a large pot of salted water to a boil. Cook the pasta until al dente. Reserve 1 cup of the cooking water and drain.
In a large skillet, heat the olive oil and butter over medium heat. Add the minced shallot and cook for 2–3 minutes, until soft and translucent.
Pour in the white wine and let it simmer for about 2 minutes, reducing slightly.
Add crème fraîche or mascarpone directly to the pan along with the lemon zest and lemon juice.
Stir and gently simmer for 2–3 minutes.
Stir in the chopped dill, capers, black pepper, and a small pinch of salt.
Add the drained linguine to the skillet and toss to coat, loosening with a splash of reserved pasta water if needed for silky coverage.
Remove the skillet from the heat.
Fold in the smoked salmon gently.
The residual warmth will soften it without cooking or toughening it. Taste and adjust seasoning with lemon or pepper.
Divide among warm bowls and finish with extra dill, lemon zest curls, or a light drizzle of good olive oil.